This application is a 371 of PCT/JP99/05314 filed Sep. 29, 1999.
The present invention relates to a transfer material, and a surface protecting sheet, which are used for preparing a molded article excellent in weather resistance, abrasion resistance, and chemical resistance; and a process for preparing a molded article excellent in weather resistance, abrasion resistance, and chemical resistance, by using them.
As a process for forming a protection coating excellent in abrasion resistance and chemical resistance on the surface of a molded article, there have been known to those skilled in the art the process in which a transfer material composed of a substrate sheet having releasing property, and a protecting layer formed thereon, is adhered to molded article so that the protecting layer faces the surface of the molded article, and the substrate sheet is then released; and the process in which a surface protecting sheet composed of a substrate sheet having no releasing property, and a protecting layer formed thereon, is adhered to a molded article so that the protecting layer faces outside, and the like.
For example, WO97/40990 describes a transfer material which is composed of a substrate sheet having releasing property, and a protecting layer consisting of a heat reactant of a heat and active energy ray curable resin composition. The publication also describes a process for forming a protection coating excellent in abrasion resistance, chemical resistance, and the like, on the surface of a molded article by using the transfer material. Specifically, the process comprises the steps of: adhering the transfer material to the surface of a molded article so that the protecting layer faces inside; releasing the substrate sheet; and irradiating the protecting layer which is transferred to the molded article with active energy ray to completely cure.
The publication additionally describes a surface protecting sheet which is composed of a substrate sheet having no releasing property, and a protecting layer consisting of a heat reactant of a heat and active energy ray curable resin composition. The publication also describes a process for forming a protection coating excellent in abrasion resistance, chemical resistance, and the like, on the surface of a molded article by using the surface protecting sheet. Specifically, the process comprises the steps of: adhering the surface protecting sheet to the surface of a molded article so that the protecting layer faces outside; and irradiating the protecting layer with an active energy ray to completely cure.
The protecting layer employed in the transfer material or the surface protecting sheet described herein, is comprised of a heat reactant of a heat and active energy ray curable resin composition. The heat and active energy ray curable resin composition means a resin composition which is curable in response to both heat and active energy ray, and does not completely cure till both the heat and the active energy ray are applied.
A heat and active energy ray curable resin composition originally may contain low molecular weight components, and it is generally tacky and flowable. However, when the heat and active energy ray curable resin composition is heated, the low molecular weight components are crosslinked and polymerized, and therefore the resulting heat reactant becomes tack free. However, the heat reactant is kept flexible because it have not yet irradiated with an active energy ray, and is in the state of semi-cured, and therefore cracks do not occur at the curved part even when the heat reactant is adhered along the surface of a molded article having complicated shape.
The transfer material or the surface protecting sheet described herein is convenient for handling because the protecting layer thereof is made of a heat reactant of a heat and active energy ray curable resin composition and is tack free, and cracks do not occur at the curved part even when adhered along the surface of a molded article having complicated shape because the protecting layer thereof is flexible.
The protecting layer may be irradiated with an active energy ray after it is placed on the surface of a molded article, and completely cured to become a protection coating excellent in abrasion resistance, chemical resistance, and the like.
On the other hand, it is known to the art that a UV absorber is added to a protection coating placed on the surface of a molded article to improve weather resistance of the molded article or the picture which is covered beneath the protection coating. For example, the above described publication sets forth that a UV absorber such as benzotriazole-type, and benzophenone-type, and the like is added to a protection coating of a transfer material, or a surface protecting sheet.
However, most of the conventional UV absorbers are low molecular weight crystalline compounds, and thereby various problems are caused. For example, the conventional UV absorber is volatilized out by heating or bled out with elapsing time because its molecular weight is low and its vapor pressure is high. As a result, it is difficult to supply sufficient long-period weather resistance to the beneath layer.
In addition, a protection coating of the surface of a molded article is generally thin, and a considerable amount of UV absorber have to be added in order to shield UV effectively. Whereas, it is known that the conventional UV absorber is poor in compatibility with a resin, and abrasion resistance and chemical resistance of the protection coating become poor when a large amount of the UV absorber is added to the protection coating. Transparency of a protection coating also generally becomes poor when a large amount of the UV absorber is added to the protection coating.
The present invention solves the above described problems. The object of the present invention is to provide a transfer material, and a surface protecting sheet, which is used for forming a protection coating excellent in transparency, weather resistance, abrasive resistance, and chemical resistance at low cost without forming cracks at the curved surface. The present invention also aims at providing a process for preparing a molded article excellent in weather resistance, abrasive resistance, and chemical resistance by using them.
The present inventors have intensively studied to solve the above described problems. As a result, they have found that the above described problems can be solved, by employing a heat and active energy ray curable resin composition which comprises, as an active ingredient, a specific polymer, polyfunctional isocyanate, and a specific UV absorber, in preparing a transfer material, or a surface protecting sheet.
That is, the protecting layer of a transfer material, or a surface protecting sheet of the present invention is composed of an active energy ray curable resin. The active energy ray curable resin is obtained by heat-crosslinking a heat and active energy ray curable resin composition which comprises, as an active ingredient, a polymer having a (meth)acryl equivalent weight from 100 to 300 g/eq, a hydroxyl value from 20 to 500 and a weight-average molecular weight from 5000 to 50000; a polyfunctional isocyanate; and a UV absorber;
characterized in that the UV absorber is a bisbenzbtriazole-type UV absorber represented by the formula: 
xe2x80x83wherein R each independently represents a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, n each independently represents an integer of 4 to 8, m each independently represents an integer of 1 to 20.
One aspect of the present invention is a transfer material which comprises at least a substrate sheet having releasing property, and the above described protecting layer formed on one surface of the substrate sheet.
Another aspect of the present invention is a surface protecting sheet which comprises at least a substrate sheet having no releasing property, the above described protecting layer formed on one surface of the substrate sheet, and an adhesive layer formed on another surface of the substrate sheet.
When a molded article excellent in abrasion resistance, chemical resistance, and weather resistance is prepared by using the transfer material of the present invention, a process comprising the steps of: adhering the transfer material along the surface of a molded article; releasing the substrate sheet to transfer the protecting layer on the molded article; and irradiating the protecting layer transferred to said molded article with an active energy ray; may be employed.
When a molded article excellent in abrasion resistance, chemical resistance, and weather resistance is prepared by using the surface protecting sheet of the present invention, a process comprising the steps of: adhering the surface protecting sheet along the surface of a molded article; and irradiating the protecting layer of the surface protecting sheet with an active energy ray; may be employed.